The purpose of the LIFE Study is to assess the impact of environmental factors, broadly defined to include lifestyle factors, on human reproduction and development. The LIFE Study is consistent with the mission of the National Institute of Child Health and Human Development that includes conducting basic, clinical and epidemiologic research focusing on factors and processes associated with human reproduction and development thereby, ensuring the birth of healthy infants capable of reaching full adult potential unimpaired by physical or mental disabilities. This study is assessing the relation between select environmental factors and human fecundity and fertility, particularly in the context of lifestyle. 501 couples discontinuing contraception for purposes of becoming pregnant were recruited from 16 targeted counties in Michigan and Texas. Couples completed baseline interviews and standardized anthropometric assessments and were prospectively followed for up to 12 months attempting pregnancy. Pregnant women were followed until delivery. Couples provided blood and urine samples at baseline, and men provided semen samples and women saliva samples for the analysis of semen quality and stress biomarkers, respectively. Select blood metals (lead and cadmium), serum organochlorine pollutants (PCBs and PFCs) and short lived (e.g., phenols, phthalates) chemicals were found to be associated with couple fecundity as measured by a longer time required for pregnancy. Male chemical concentrations were observed to be associated with greater reduction in fecundity. Other persistent chemicals such as PFCs were associated with select semen quality endpoints as were other short lived chemicals such as specific phthalates and UV-type BP filters.